Method of wet magnetic separation



April 25, 1939. Q 'PAYNE 2,156,125

METHOD OF WET MAGNETIC SEPARATION Filed March so, 1937 2 Sheets-Sheetl15 E E l April 25, 1939. c. Q. PAYNE METHOD OF WET MAGNETIC SEPARPTION 2Sheets-Sheet 2 Filed Mach 30, 1957 YNE INIVIENTOVR (ma /v05 Q.

' Patented Apr. 25, 1939 UNITED STATES PATENT- OFFICE 1 Claim.

This invention relates to a method of wet magnetic separation of oresand minerals, especially those which are finely divided, and isapplicable to the separation both of strongly and also of feeblymagnetic minerals.

An important object of the invention is to control the gravitational andelectrostatic forces which tend to interfere with magnetic attractionexerted on the particles while they are underlO going separation. Thisis accomplished by feeding the mixed particles in the form of a waterdiluted feed-stream into a water filled tank, then thickening thefeed-stream as it descends to a submerged magnetic field in the tank byremoving a practically clear-water over-flow from the top of the tankand at the same time regulating the descent of the thickened pulp bycontrolling the,

areas of the discharge outlets for the separated products at the bottomof the tank so that the velocity of descent through the magnetic fieldwill be sumciently reduced for the deflection of feebly magneticparticles while passing therethrough.

Other objects and advantages of the-invention will appear as thedescription proceeds.

The accompanying drawings show two forms of magnetic separators forcarrying out my improved method.

Fig. 1 is a vertical section of a separator which uses a single magneticfield on two flux circuits.

Fig. 2 is a vertical. section on the line II-II of Fig. 1.

Fig. 3 is a horizontal section with parts broken away on the lineIII-III of Fig. 1.

Fig. 4 is an enlargedperspective view of portions of interleavedmagnetic and nonmagnetic rotor disks, having. open longitudinal groovesalong their circumferences.

Fig. 5 is a perspective view of a modified form 0 of magnetic andnonmagnetic disks with longitudinal grooves filled with nonmagneticmaterial.

Fig. 6 is a vertical section through a modified form of a double-passseparator along the line VI-VI of Fig. 8 having superposed electromag- 5nets, each having two magnetic fields on a single fiux circuit.

Fig. 7 is a horizontal section along the line- VII-VII of Fig. 6.

Fig. 8 is a longitudinal sectional elevation on the line vm vm of Fig.6. 1

Ores and minerals, especially when finely divided as in the case ofclays, slimes, or those crushed to pass about one hundred mesh screen orfiner, present serious difiiculties to their mag- 'netic separation.when they are in the dry state.

. GIGS.

This may be briefly explained as due toenmeshment or clotting. It maybecaused either by absorption of moisture from the atmosphere, or byimpressed forces such as an electrostatic charge between minerals ofdifferent composition when they are moved upon each other. In eitherfeed and wash-water to hasten the passage of the ore through themagnetic field.

The purpose of the method of wet separation herein set forth is togreatly enlarge the scope and value of inductive magnetic separation bypermitting ores to be treated which have not In all cases however, freeuse is made of This method while capable of exerting the utmostattracting force upon the feed-stream as it passes through the submergedmagnetic field-gap is also able to control the velocity of descent ofthe latter and therefore also the separating force, by eliminating thefeed water by overflowing it as it enters the tank in which theseparation takes places. Dealing in this way with the regulated speed ofsubsidence of fine particles in water. it is possible to attract andseparate, more easily, those feebly magnetic minerals such as ironsilicates, hornblende, biotite, garnet, etc. which can only be acted onwhen fine, by careful adjustment between the attracting and separatingforces. Freedom of motion of the particles among themselves is thusassured, and their effective.

weight is reduced by the amountof water which they displace. In effecttheir resistance to separation is thus reduced when submerged. It alsopermits those tiny occluded and middling par ticles to be'defiected andseparated to a much greater degree than has heretofore been possible bymeans of dry separation.

In the form of magnetic separator illustrated shaft II belowthe'electromagnets. The shaft I1 is driven from a pulley I8. Thelaminated diskrotor I3 forms the armature of the electromagnets andserves also as a separating drum on which the material to be separatedis fed from a 'water filled hopper I9 placed above it. The

rotor I3 revolves between concentric faces of the pole pieces I2 withsubstantially equal gap on each side in order to balance the magneticattraction of the pole pieces. The width of the field gap between thepole pieces i2 and rotor 93, in which the separation takes place, isregulated to suit the size of the particles to be separated and is asnarrow as practicable to reduce the reluctance of the magnetic circuit.The electromagnets it) are connected to the current supply so that oneyoke will convey. only north magnetism to one pole piece, while theother yoke conveys only south magnetism to the other pole piece. In thisway a single magnetic field is .formed upon two flux circuits as shownby the broken lines and arrows in Fig. 3. The thickness of the magneticdisks 4D and nonmagnetic disks 4i forming the rotor I3 will depend uponthe size of the ore particles to be separated. They are provided withhorizontal grooves 42 along their circumference in order to increasetheir holding power by means of. the highly convergent magnetized pointsat the groove intersections as well as at the groove and disk edgesthemselves, as shown in Fig. 4-. These horizontal grooves may be closedby means of nonmagnetic strips B3, as shown in Fig. 5, where it isimportant to give the rotor a smooth outer surface. The horizontalgrooves may also be left open as shown in Fig. 4 where itis desirable toafford some support for the particles undergoing separation as they arecarried through the field-gap. The rotor shaft I1 is supported instufiing-box bearings 20, which are attached to nonmagnetic cheek-plates2I at each end of the rotor. These fit water tight to the ends of thepole pieces I2 and with the pole pieces form the central portion of thetank'in which the separation takes place. It is desirable to protect thesurface of the rotor and the faces of the pole pieces with chromium orcadmium plating to prevent rusting. The hopper I9 forming the upper partof the water tank is detachable and has its upper edge surrounded by acontinuous trough 22. the overflow from the dilute feed pulp to becollected and discharged to one side. Above the main hopper is a smallerpartly submerged V- hopper 23 which is supported upon the upper edge ofthe main hopper. This smaller feed hopper 23 is of about the same lengthas that of the rotor, and a plate 24 underlies its discharge opening.The plate 24 deflects the feed-stream of materials to be separated whichis discharged in thin sheets 24a towards both sides of the main hopperand enables the feed-water which is introduced with the ore str'eam, torise and overflow the top of the main hopper as practically clear waterwhile the thickened pulp descends in a. disseminated cloud through theupper part of plates 25 and 26 and is fed to the charged rotor Thisenables I3 which revolves in the direction shown by the arrow in Fig. 1.The nonmagnetic particles descend along the stationary side of the fieldgap and fall vertically 28 when they are released and discharged as theyapproach the neutral plane of the rotor where all attractive force ofthe rotor ceases,

' owing to reversal of polarity. They are then deflected at a divergentangle from the non-magnetic particles and fall vertically on the otherside of the division plate into, a separate hopper 29 thus efiectingtheir separation from the latter. I

A brush or scraper 30 serves to dislodge fine steel particles sometimespresent in the ore and carried past the neutral line. The receivinghoppers 27 and 29 are bolted water tight to the bottom of the tank whichcontains the disk rotor.- At the discharge ends of these hoppersplug-cocks 3| and 32 are located whose openings can be closelyregulated. By varying the openings of these valves 3| and 32 theseparated products obtained from the thickened feed-pulp can bedischarged either slowly or else rapidly from the separator as thenecessity of the material undergoing separation may! require. As afurther means of regulating and equalizing the velocity 1' of thedownward water current through the fieldgap it is advisable to providebafiles 33, 34 in the upper part of each of these hoppers.

When the field coils of the electromagnets have been energized to securethe required magnetic I- fiux across the field gap, the rotor is causedto revolve in the direction shown by the arrow..

The material to be separated is then fed below the water level of themain hopper tank by means of the small distributing V-hopper 23. Thematerial is thus enabled to free itself more readily from the feed-waterwhich accompanies it and the greater part of the feed water dischargesover the top edge of the main tank into the trough 22 as practicallyclear water. In some cases where the finely ground material is very muchdiluted, it may be advisable to employ an intermediate settling tank inorder to thicken the pulp before feeding it to the separator; In certaincases as in treating clays, it may also be advisable to add anelectrolyte to the separator feed tank, such as sodium chloride orcaustic starch, in order toremove cloudy suspensions and to hasten thesettling of the fine particles. As they descend, the particles arecollected by the guide plates 25 and 26 and are fed upon the rotor I3.The magnetic particles are attracted and held to the charged edges andpoints of the rotor until they are carried over the edge of the divisionplate 28.

The nonmagnetic particles on the other hand pass through the field-gapwithout being deflected, and are collected in a separate hopper whosedischarge rate is controlled by means of the plugcock 32. of feed, thespeedof the rotor and strength of the fieldpboth the attracting and theseparating forces can be brought under closer control than hasheretofore been possible, especially in the case of finely divided oresand minerals.

A modification of the design of separator described above and itsapplication to the separation of finely divided materials into threeproducts by means of two superposed electromagnets is illustrated inFigs. 6, 7 and 8. In this form of embodiment of my invention, bipolarelectromag- In this way and byvarying the rate nets 5B and 52 are shownm Fig. 6 in their superposed position, each of which has two rotors 5|,5m, 53 and 53a mounted on shafts 56 and 51. These are so assembled withsingle yokes 54 and 55 that with the aid of keepers 83 and 84 theysecure two magnetic fields upon the same flux circuit generated by theelectromagnets as shown in Fig. 7. In this design the iron path of theflux circuit can be made somewhat shorter in relation to the length offield-gap available for separation, than in the design shown in Figs. 1,2 and 3. The

two electromagnets 5G and 52 may be energized to produce a cleanmagnetic concentrate 58 from the top electromagnet 50 and a cleantailings 59 and middlings product 80 from the bottom electromagnet 52.The two successive magnetic products may also be combined where they areto be discarded, and where the main object is to secure a cleannonmagnetic product from the crude material by means of a double pass asillustrated in Fig. 6.

The mechanical features in the form of sepa rator illustrated in Figs.6, 7 and 8 may differ from that illustrated in Figs. 1, 2 and 3 in thatthe partly submerged V-hopper 6| here has a feed roller 62 underlyingits discharge opening in place of plate 24 illustrated in Fig. 1. Thefeed rollers 62 and 62a revolve with the shaft 63 and deflect thefeed-stream of the materials to be separated in such manner that it isdischarged in a thin sheet 64 toward the inclined portion 65 of the mainhopper. It then falls to the inclined guide plate 66 from which it isfed to the upper charged rotor 51 or 5| a which revolves in thedirectionshown by the arrow in Fig. 6.

The particles which are not attracted by the magnetized edges and pointsof disks 40 of rotors 5| and 5 la fall vertically into the hopperedopening formed by the inclined plates 61 and 68. These are supportedabove rotors 53 and 53a and guide the particles upon the lower charged mtors 53 and 53a. which separate the remaining magnetic particles fromthe material which has been fed to them. The nonmagnetic portiondescends into hopper 69, while the magnetic portion of the material isdischarged over the division plate 10 as the rotor 53 or 53a. loses itspower of attraction at the neutral line due to reversal of polarity.

The particles 58 which have beenattracted and deflected by the energizedrotors 5| or 5M.

and carried over division plate 12 may also be collected in hopper I5along with magnetically attracted particles 60 which have been separatedfrom the nonmagnetic particles 59 by the lower set of rotors 53 or 530where only two separated products are desired.

The separating rotors in the form illustrated in Figs. 6, '7 and 8 maybe revolved by a chain drive connecting the sprocket wheels amxed to therotor shafts and the counter-shaft 16 which in turn is driven by thepulley 82. Feed-roller shaft 63 is drivably connected to counter-shaft16 by means of sprocket wheel 17, an endless chain 18 and a sprocketwheel mounted on feed-roller shaft 63. Sprocket wheel I8 which ismounted on counter shaft I5 is drivably connected with rotor shaft 56 bymeans of a drive chain 19 and a sprocket wheel mounted on said rotorshaft. Another sprocket wheel mounted on shaft 55 serves to drive rotorshaft 51 with the aid of an endless chain and sprocket wheel 8| mountedon shaft 51. By varying the relative size of these sprocket wheels, thespeeds of the various rotors may be varied to suit the nature of thematerial to be separated.

The principle involved in both the above described designs is, however,the same. The dilute feed-stream is fed into the top of a water filledtank and is thickened as it descends to the submerged magnetic fields byremoving a practically clear-water overflow from the top of the tank.The actual separation of the nonmagnetic from the magnetic particles isaccomlished by one or more energized rotors, in the tank. while thespeed of descent of the thickened feedstream is controlled by varyingthe areas of the discharge outlets for the separated products at thebottom of the tank.

I wish it to be understood that my invention is not limited to acombination of the specific elements or to the specific structuresillustrated in the drawings, but that" it includes all such variationsas come within the spirit and scope of the disclosure herein and theclaim appended hereinafter.

I claim:

The method of wet magnetic separation of ores and minerals containingfeebly magnetic and nonmagnetic particles which consists in submergingthem in a tank of water thereby reducing their eifective weight, causingthe particles of ore to fall through the water and along guide platesinto a submerged arcuate magnetic field gap formed between an arcuatefaced pole piece and a" horizontal magnetic rotor submerged in said tankand attracting the magnetic away from thenonmagnetic particles withinsaid gap by feeding them along the arc of said horizontal rotor indirect contact therewith in said magnetic field, substantially as andfor the purpose described.

. CLARENCE Q. PAYNE.

